oss-sec mailing list archives
CVE-2023-49284: fish command substitution output can trigger shell expansion
From: Alan Coopersmith <alan.coopersmith () oracle com>
Date: Fri, 8 Dec 2023 10:54:02 -0800
https://github.com/fish-shell/fish-shell/security/advisories/GHSA-2j9r-pm96-wp4f reports: Package: fish-shell Affected versions: < 3.6.2 Patched versions: 3.6.2 CVSS: 3.9 (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L) CVE ID: CVE-2023-49284 Impact:fish shell uses certain Unicode non-characters internally for marking wildcards and expansions. It will incorrectly allow these markers to be read on command substitution output, rather than transforming them into a safe internal representation.
While this may cause unexpected behavior with direct input (for example, echo \UFDD2HOME has the same output as echo $HOME), this may become a minor security problem if the output is being fed from an external program into a command substitution where this output may not be expected.
Consider the following: In foo.py:print("\ufdd2HOME") # Perhaps this value is retrieved from a database or external source
At the shell: > echo $(python3 foo.py) /home/fishuserThis design flaw was introduced in very early versions of fish, predating the version control system, and is thought to be present in every version of fish released in the last 15 years or more, although with different characters.
Code execution does not appear to be possible, but denial of service (through large brace expansion) or information disclosure (such as variable expansion) is potentially possible under certain circumstances.
Patches: fish shell 3.6.2 has been released to correct this issue. -- -Alan Coopersmith- alan.coopersmith () oracle com Oracle Solaris Engineering - https://blogs.oracle.com/solaris
Current thread:
- CVE-2023-49284: fish command substitution output can trigger shell expansion Alan Coopersmith (Dec 08)